Control for combustion apparatus



May 2 1944. J. w. MILLER CONTROL FOR COMBUSTION APPARATUS Filed Jan. 19, 1942 I 3 M w 8 W 4 2 9/ 3 4 4 4 /9 ll 4 5 5 4 4 v\J/ 4 3 al.-v 5 a... F z 6 0 m 2 2 Y INVENTOR. JOHN W. MILLER.

FIG.2

Patented May 2, 1944 CONTROL ron COMBUSTION APPARATUS John W. Miller, Lansing, Mioh., assignor to Motor Wheel Corporation, Lansing, Mich., a

corporation of Mic Application January 19, 1942, Serial No. 421,229

- 3 Claims.

apparatus provision should be made for varying the heat output of the apparatus and for utilizin the air circulating fan for cooling in the summer time. The principal object of the present invention is the provision of a novel and simple control system for accomplishing these results.

According to the herein disclosed form of the present invention, fuel is fed to the burner through a valve operable between predetermined closed and opened positions under the control of a room thermostat. In order to vary the heat output, provision is made for adjusting the closed position so'that the burner is operated either between a high fire and a pilot fire, or between a high fire and a low fire. This adjustment is accomplished by an electric. heat motor which is controlled by a manual switch located on the room thermostat.

During the heating season the air circulating fan is under the control of a temperature responsive switch arranged in heat exchange relation to th interior of the heat chamber. In

order that the fan may be 1 38d for cooling inthe summer time, a second switch is arranged in parallel relation to the said temperature responsive switch so that the fan can be operated by closing either of the switches.

In order to minimize the amount of wire used -and also to prevent operating the fan in the winter time, when the heat is not on, common means are provided for selectively controlling the manual operation of the fan and the adjusting motor for the valve. Thus, in the winter time, only the valve adjusting motor is under the control of the manual switch located on the room thermostat; while in the summer time, only the fanmotor is under the control of this operating switch.

This operating means comprises a control circuit including a motor for operating the fan circuit switch, the motor for adjusting the'closed position of the fuel valve, and common means (including the manual switch on the thermostat) for selectively energizing one or the other of said control circuit motors. s

For a more detailed statement of the invention and a more complete understanding of the a heating coil ll.

advantages thereof, reference should now be had to the accompanying drawing, wherein:

Figure 1 is a diagrammatic illustration of a furnace and the controls therefor; and

Figure 2 is a fragmentary cross-sectional view of a fuel regulator employed in the furnace shown in Figure 1.

The invention is illustrated in the drawing as applied to a warm air furnace having a forced air circulating system. The heating system comprises a furnace Ill having a heat exchanger ll of conventional form. In the lower part of the .heat exchanger is an oil burner l2 of the vaporizing pot type. Fuel oil is fed to the burner from a source of supply (not shown) through a fuel control 13 which regulates the rate of flow of fuel to the burner.

The fuel control I3 comprises a housing having a fuel chamber 36 in which fuel is maintainedat a constant level by means-of a float valve or barometric tank of conventional form (not shown). In the bottom of the chamber is an outlet opening in which a fuel valve 31 is reciprocable vertically. A heat motor 38 is provided for moving the fuel valve between its open and closed positions. -The heat motor comprises a bimetal strip fixed at one end to the housing. The other end is adapted to engage the fuel valve 31. The bimetal strip is surrounded by a heating coil 39 and is so arranged that when cold the strip permits the valve to move toward closed position, and when heated by the coil 39 the strip bends and moves the valve to its open position.

Another heat motor 40 is provided for adjusting the closedposition of the fuel valve 31. It comprises a bimetal strip surrounded by This heat motor 40 is so arranged that when cold it permits the valve 31 .to substantially completely close, but when heated by the coil 4| the bimetal strip moves the valve 31 to a partially opened position and prevents the valve fromclosing. Thus, when the coils 39 and 4| are both de-energized, and therefore, not furnishing heat to the respective bimetal strips, the valve 31 is nearly closed. In this position a very slight quantity of fuel is permitted to flow into the burner to maintain a very small flame called pilot fire. When the coil 39 is energized it heats the bimetal strip therein and moves the valve 31 to its wide open position. This permits the fuel to flow at its greatest rate and maintain a high fire. When the coil ll is energized the valve is opened somewhat above its pilot fire position but considerably lower than its high fire position. This position is termed "low fire" and some heat is thereby furnished at all times. Energization of coil 39 during the time the coil 4| is energized will open the valve 31 to its wide .open position and maintain a high fire.

Surrounding the heat exchanger is a jacket l4 having a plurality of warm air ducts I5 issuing from the top thereof. Air is circulated through the jacket Id and the heated space by a. centrifugal fan Hi. The fan is driven by an electric motor I1.

The electric system which controls the operation of the fuel regulator and the fan may be considered as two circuits, the fan circuit and the control circuit. The fan circuit comprises the motor l1, one terminal of which is connected by a conductor 18 to oneside of the usual 110 volt line. The other terminal of the motor I1 is connected by conductor l9 to one terminal of a. switch 20. The other terminal of the switch 20 is connected by conductor 2| to the other side of the line. The switch 20 is actuated by thermo-responsive element 22, such as a bimetal strip, located in the furnace jacket adjacent the heat exchanger H. The element 22 is subject to the temperature of the air within the heat exchanger and bends one way or the other, depending upon the variation in the temperature of 'the heat exchanger. The switch 29 is arranged so as to be closed and thereby complete the fan circuit when the temperature of the heat exchanger increases to a "predetermined point. The switch opens, and thereby stops the fan,

when the temperature drops below a predetermined point.

Another switch 23 is connected in parallel with the switch 20 by conductors 24, 25 and 28, so that when either of the switches 20 or 23 is closed the fan is actuated. The switch 23 is closed by the action of a switch motor 21, preferably in'the form of a solenoid which will be more fully described later.

The control circuit comprises the heat motors 38 and 40, a safety or limit switch 28, a room temperature thermostat 29, on operating switch 30, a single pole double throw selecting switch 3|, the secondary 33 of a step down transformer 32, switch motor 21, and suitable conductors. The primary 34 of the transformer 32 is connected to the 110 volt line by conductors 26 and 35. Preferably the voltage of the secondary of the transformer is 12 volts.

One terminal of the heating coil 39 or the heat motor 38 is connected by a conductor 42 to one terminal of the switch 23. This switch is a. limit switch and normally is closed. It is opened only when the temperature of the heat exchanger exceeds a safe limit. The other terminal of the switch 28 is connected by conductors 43 and 44 to one terminal of the secondary 33 01' the transformer. The other terminal of the coil 39 is 60 connected by a conductor 45 to one terminal of the thermostat 29 while the other terminal of the thermostat is connected by conductor 46 to the other side of the transformer secondary 33. Thus, whenever thermostat 29 is closed the coil 39 is energized and becomes warm.

One side of the heating coil M of the heat motor '40 is connected by the aforementioned conductors 42, 43 and 44, and switch 28 to one side of the transformer secondary 33, while the other side of the coil 4| is connected by conductor 41 to terminal W of the selecting switch 3|. The switch 3| is connected by conductor 48 to an operating switch 30 which in turn is connected by conductors 49 and 45 to the transformer secondary. Preferably the operating switch 30 is mounted on, or in the housing that contains the thermostat 29.

The third terminal S of the selecting switch 34 5 is connected by conductor 59 to the switch motor 21 above mentioned that operates the fan switch 23. The other side of the switch motor 21 is connected by conductors 5| and 44 to the transformer secondary.

When the apparatus above described is to be used for heating, the selecting switch 3| is thrown to the dotted line position in Figure 1, so that it contacts the terminal W; The pilot of the burner is lighted, and if the weather is reasonably mild the operating switch 30 is opened.

The circuit of-the coil 4| for the motor 40 is then open and the coil is deenergized. Accordingly, the burner operates on pilot fire until such time as the room in which the thermostat is located calls for heat. When that occurs, the thermostat 29 closes and the circuit of the coil 39 through the conductors 42, 43, 44, 46 and 45, switch 28 and thermostat 29 is closed. That energizes the coil 39 of the heat motor 38, opening the valve 31 to its wide open position. The fire rises to its maximum output, or high fire stage, and increases the temperature of the heat exchanger ll. When the temperature of the heat exchanger ll reaches a predetermined point it causes the bimetal element 22 to bend and close switch 20 to turn on the fan IS. The

fan then circulates warm air through the heating ducts 15. When the air in the room reaches the predetermined temperature for which the 5 thermostat 29 is set, the thermostat opens, the

coil 39 is deenergized, and the valve 31 is permitted to close, whereupon the fire drops to pilot condition.

If the weather is colder and it is desirable to maintain some heat in the heat exchanger at all times so as to reduce the warm up period, the operating switch 30 is closed. That energizes the coil 4|, causing motor 40 to open the valve 31 to low fire position in the manner described above. There the valve 31 remains until the room calls for heat, whereupon the thermostat 29 closes and causes the valve 31 to open to its high fire position in the manner previously described.

Thus, it will be seen that when the apparatus is operated as a heating unit the fuel regulating valve 31 is moved between pilot and high fire positions by the thermostat 29 during mild weather when switch 30 is open, and the valve 31 is moved between the low fire position and high fire position during periods of more severe temperatures when switch 30 is closed. Either of those'ranges of movement of valve 31 can be se-' lected by means of the operating switch 30. In either case the fan is operated automatically when the heat exchanger reaches a predetermined temperature and is stopped when the heat exchanger goes below a predetermined temperature.

In the summer the heating system is entirely -inoperative, but it may be desirable to use the fan to circulate the air during extremely warm weather. Therefore, when the heating plant is shut down, the double throw selecting switch II 70 is thrown to the summer position marked 8. This disconnects the operating switch 30 from the circuit of the heat motor 40 and places it in the circuit or the switch motor 21. Then, when it is desired to use the fan as a cooling device the switch 30 is closed- That completes the 01:

cuit through the conductors l6, l9, I8, 50, SI and M, switches 30 and 3|, and switch motor 21. Switch motor 21 closes switch 23, thereby completing the circuit of the motor I! to operate the fan IS. The fan may be stopped at any time by opening the switch 30, thereby deenergizing the switch motor 2'! and permitting the switch 23 to open.

While in order to minimize the possibility of inadvertently operating the fan when it is desired to operate the heat motor 40, or vice versa, two switches 20 and 3| are employed, it will be evident that but one switch need be used. A single, double throw, selector switch, such as the switch 3i, can be employed in place of switch 30. The switch should have a neutral,,or oif position to which the switch is thrown when neither motor 21 nor motor 40 is to be energized. The terminals at the two operative positions of the switch are connected to the motor 21 and motor 40 respectively.

From the foregoing it will be seen that this invention provides for the partial control of the heating system in winter and control of the fan in summer by means of a single switch, which is conveniently located adjacent the thermostat. The switch thus serves two purposes. Since the selecting switch 3i need be actuated but twice a year, once in the spring and once in the fall. it can be located near the other furnace controls, even though that location be inconvenient, thereby reducing the amount 01' additional wiring necessary.

The scope of the invention is indicated in the appended claims.

I claim:

1. A control system for combustion apparatus comprising, in combination: a fuel valve operable between predetermined opened and closed positions; a first motor associated with said valve for moving the latter between said predetermined positions; a second motor associated with said valve for limiting in one direction the movement of the valve imparted thereto by the first motor; an air circulating fan associated with said com bustion apparatus for supplying air to the latter and a motor for operating said fan; a circuit for said first motor; a circuit for said second motor; and a control circuit for said fan motor including means common to both of said last named circuits for selectively closing one or the other of said circuits.

2. A control system for combustion apparatus comprising, in combination: a fuel valve operable between predetermined opened and closed positions; a first motor associated with said valve for moving the latter between said predetermined positions; a second motor associated with said valve for limiting in one direction the movement of the valve imparted thereto by the first motor; an air circulating fan associated with said combustion apparatus for supplying air to the latter and amotor for operatingsaid fan; a circuit for said first motor; a circuit for said second motor; a circuit for said fan motor including a switch; an electric relay for operating the switch in the fan motor circuit; a circuit for said relay; said relay circuit and said second motor circuit including common means for selectively closing one or the other of said last mentioned circuits.

3. A control system for combustion apparatus comprising, in combination: a fuel valve operable between predetermined opened and closed positions; a first motor associated with said valve for moving the latter between said predetermined positions; a second motor associated with said valve for limiting in one direction the movement of the valve imparted thereto by the first motor; an air circulating fan associated with said combustion apparatus for supplying air to the latter and a motor for operating said fan; a circuit for said first motor; a circuit for said second motor; a circuit for said fan motorincluding a switch; an electric relay for moving said switch from opened to closed position and a circuit for said relay; said relay circuit and said second motor circuit including a common two position switch for selectively closing one or the other oi said circuits and another switch in series with said two position switch.

JOHN w. MILLER. 

